In general, a variety of resins are employed as the material for containers of seasonings, oils, beverages, cosmetics, detergents and the like, in accordance with the type of the content matter to be filled and the purpose of use.
Among these polyester resins, polyethylene terephthalate has excellent mechanical strength, heat resistance, transparency and gas barrier property, and thus is suitable as the material for containers holding beverages such as juices, soft drinks, carbonated beverages and the like in particular. For the container for beverages, hollow bottles obtained by blow molding polyethylene terephthalate are normally used.
When a beverage is sterilized by heating and filled in a bottle, the bottle is required to have heat resistance. Specifically, the bottle is required not to undergo deformation or change in capacity when a liquid of high temperature is filled therein. In order to impart heat resistance to a bottle, a method of enhancing the density of the bottle body portion by heating the mold used in stretch blow molding to a temperature of, for example, 130° C. or greater to subject the bottle to heat treatment (heat setting), is disclosed in, for example, Patent Document 1 or Non-Patent Document 1, p. 653. However, there still is a demand for a bottle having better heat resistance.    [Patent Document 1] JP-A-4-97820    [Patent Document 2] JP-A-5-200842    [Non-Patent Document 1] “Saturated Polyester Resin Handbook”, Yuki, Kazuo, Ed., Nikkan Kogyo Shimbun, Ltd. (1989)